Update branding to preview1 (#39661)

Author: wtgodbe

eng/Versions.props

@@ -16,8 +16,8 @@
     -->
     <StabilizePackageVersion Condition="'$(StabilizePackageVersion)' == ''">false</StabilizePackageVersion>
     <DotNetFinalVersionKind Condition="'$(StabilizePackageVersion)' == 'true'">release</DotNetFinalVersionKind>
-    <PreReleaseVersionLabel>alpha</PreReleaseVersionLabel>
-    <PreReleaseBrandingLabel>Alpha $(PreReleaseVersionIteration)</PreReleaseBrandingLabel>
+    <PreReleaseVersionLabel>preview</PreReleaseVersionLabel>
+    <PreReleaseBrandingLabel>Preview $(PreReleaseVersionIteration)</PreReleaseBrandingLabel>
     <IncludePreReleaseLabelInPackageVersion>true</IncludePreReleaseLabelInPackageVersion>
     <IncludePreReleaseLabelInPackageVersion Condition=" '$(DotNetFinalVersionKind)' == 'release' ">false</IncludePreReleaseLabelInPackageVersion>
     <AspNetCoreMajorMinorVersion>$(AspNetCoreMajorVersion).$(AspNetCoreMinorVersion)</AspNetCoreMajorMinorVersion>